A common foundry induction furnace typically comprises a cylindrical furnace wall including an induction heating coil, and a continuous lining formed of sintered silica or other refractory material defining a chamber for containing molten metal, such as iron melt. From time to time, the lining becomes eroded and requires replacement. Following removal of the worn lining an expendable steel cylindrical form is concentrically installed within the furnace. The outer surface of the form is spaced apart from the inner surface of the furnace so as to define an annular space therebetween. Refractory particulate material is then manually poured into the annular space. Once the annular space has been filled, the refractory material is sintered first by gas heaters fired into the furnace, and thereafter by an initial charge of molten iron melted within the furnace. The initial charge also melts the expendable form to reveal the sintered lining.
Manual pouring of the refractory material into the annular space is strenuous, labor intensive work. Workers are required to wear protective clothing and use respirators to guard against airborne particulate dust that may pose health risks. Foundries are under increased pressure to operate within environmental guidelines, and therefore, manual pouring of refractory material has become increasingly undesirable. In addition, during manual pouring of the refractory material air tends to be entrapped in the particulate material resulting in voids in the lining that physically weaken the lining or create pockets of over heated metal. Human variability, such as inexperience and fatigue, results in inconsistencies in the lining, which lead to unpredictable refractory life and production schedules from one lining to the next.
To deal with the problems associated with manual pouring of refractory material, an automated particle dispensing apparatus has been considered and is disclosed in U.S. Pat. No. 5,058,776. Although this apparatus produces more consistent linings than the manual method, it has been found that when pouring refractory material having fine grain sizes of particulate material the apparatus does not always deliver a smooth flow of refractory material into the annular space. This can result in an uneven distribution of particulate material, which may produce a substandard lining.
It is therefore an object of the present invention to provide a particulate dispensing apparatus that obviates or mitigates the above disadvantages.